Kinesiology of the Hip Joint and Pelvic Girdle

Pelvic Girdle Structure and Components

• The Pelvic Girdle Framework:     * Consists of the pelvic bones and the sacrum.     * There are two pelvic bones (Right and Left).

• Divisions of the Pelvic Bone:     * Ilium: Comprises the upper $2/5$ of the bone.     * Ischium: Comprises the posterior and lower $2/5$ of the bone.     * Pubis: Comprises the anterior and lower $1/5$ of the bone.

• The Sacrum and Coccyx:     * Sacrum: An extension of the spinal column consisting of $5$ fused vertebrae.     * Coccyx: Extends inferiorly from the sacrum.

Pelvic Bony Landmarks

• Anterior Landmarks:     * Iliac Features: Iliac crest, Iliac fossa, Anterior Superior Iliac Spine (ASIS), and Anterior Inferior Iliac Spine (AIIS).     * Pubic Features: Pubis ramus (Inferior and superior) and the Pubic crest.     * Ischial Features: Ischial tuberosity.     * Openings: Obturator foramen.

• Posterior Landmarks:     * Iliac Features: Posterior Superior Iliac Spine (PSIS), Posterior Inferior Iliac Spine (PIIS), and the Greater sciatic notch.     * Ischial Features: Ischial spine and the Lesser sciatic notch.

Bony Landmarks of the Femur and Lower Leg

• The Femur:     * Head and Femoral neck.     * Greater trochanter and Lesser trochanter.     * Intertrochanteric line.     * Linea aspera.

• Associated Structures:     * Patella.     * Proximal Tibia/Fibula:         * Medial tibial condyle and Lateral tibial condyle.         * Gerdy’s tubercle.         * Head of fibula.         * Tibial tuberosity.

Joints and Ligaments of the Pelvis and Hip

• Anterior Junction: Symphysis pubis.

• Posterior Junction: Two sacroiliac joints.     * Characteristics: Strong ligaments unite these bones to form rigid, slightly movable joints.

• Hip Joint (Acetabular Femoral):     * Formed by the Head of the femur and the Acetabulum.     * Type: Ball and socket joint.     * Stability Factors: Relatively stable due to bony architecture, strong and dense ligaments/capsule, and large supportive muscles.     * Function: Weight-bearing and locomotion, enhanced by a wide Range of Motion (ROM).

• Major Ligaments:     * Iliofemoral ligament (also known as the Y ligament).     * Pubofemoral ligament.     * Teres ligament.     * Ischiofemoral ligament.

• Joint Components:     * Joint capsule.     * Labrum (Acetabulum socket).     * Femoral head (Ball).

Nerve Roots and Muscle Innervation

• Lumbar and Sacral Plexus (Lumbosacral Plexus):     * Iliopsoas: Rooted at $(L2-4)$; performs Hip Flexion and External Rotation.     * Pectineus: Rooted at $(L2-4)$; performs Hip Flexion, Adduction, and External Rotation.     * Sartorius: Rooted at $(L2-3)$; performs Hip Flexion, External Rotation, Hip Abduction, Knee Flexion, and Knee Internal Rotation.     * Rectus Femoris: Rooted at $(L2-4)$; performs Hip Flexion and Knee Extension.     * Adductor Brevis: Rooted at $(L3-4)$; performs Hip Adduction, External Rotation, and Hip Flexion.     * Adductor Longus: Rooted at $(L3-4)$; performs Hip Adduction and Hip Flexion.     * Gracilis: Rooted at $(L2-4)$; performs Hip Adduction, Internal Rotation, Hip Flexion, and Knee Flexion.     * Obturator Externus: Rooted at $(L3-4)$; performs Hip External Rotation.     * Adductor Magnus: Rooted at $(L2-4)$; performs Hip Adduction, External Rotation, and Hip Extension.     * Semitendinosus: Rooted at $(L5, S1-2)$; performs Hip Extension, Internal Rotation, Knee Flexion, and Knee Internal Rotation.     * Semimembranosus: Rooted at $(L5, S1-2)$; performs Hip Extension, Internal Rotation, Knee Flexion, and Knee Internal Rotation.     * Biceps Femoris Long Head: Rooted at $(S1-3)$; performs Hip Extension and External Rotation.     * Biceps Femoris Short Head: Rooted at $(L5, S1-2)$; performs Knee Flexion and Knee External Rotation.     * Gluteus Medius: Rooted at $(L4-5, S1)$; performs Hip Abduction, Internal Rotation (anterior fibers), and External Rotation (posterior fibers).     * Gluteus Minimus: Rooted at $(L4-5, S1)$; performs Hip Abduction and Internal Rotation.     * Tensor Fasciae Latae: Rooted at $(L4-5, S1)$; performs Hip Flexion and Abduction.     * Gluteus Maximus: Rooted at $(L5, S1-2)$; performs Hip Extension, External Rotation, and Abduction.     * Quadratus Femoris: Rooted at $(L4-5, S1)$; performs Hip External Rotation.     * Obturator Internus: Rooted at $(L4-5, S1-2)$; performs Hip External Rotation.     * Gemellus Superior: Rooted at $(L5, S1-2)$; performs Hip External Rotation.     * Gemellus Inferior: Rooted at $(L4-5, S1-2)$; performs Hip External Rotation.     * Piriformis: Rooted at $(S1-2)$; performs Hip External Rotation.

Movement Classifications

• Hip Joint Movements:     * Flexion and Extension.     * Abduction and Adduction.     * External Rotation and Internal Rotation.     * Testing variants: Straight Leg vs. Knee Bent.

• Pelvic Girdle Movements (Tilts and Rotations):     * Anterior Pelvic Rotation (Tilt): Forward movement of the pelvis.     * Posterior Pelvic Rotation (Tilt): Backward movement of the pelvis.     * Left Lateral Pelvic Rotation (Tilt): Pelvis tilts to the left (viewed from the posterior).     * Right Lateral Pelvic Rotation (Tilt): Pelvis tilts to the right.     * Left Transverse Pelvic Rotation: Superior view shows rotation toward the left.     * Right Transverse Pelvic Rotation: Superior view shows rotation toward the right.

Motions Accompanying Pelvic Rotation

• Anterior Rotation (Tilt): Accompanied by Lumbar Extension, Right Hip Flexion, and Left Hip Flexion.

• Posterior Rotation (Tilt): Accompanied by Lumbar Flexion, Right Hip Extension, and Left Hip Extension.

• Right Lateral Rotation (Tilt): Accompanied by Left Lumbar Lateral Flexion, Right Hip Abduction, and Left Hip Adduction.

• Left Lateral Rotation (Tilt): Accompanied by Right Lumbar Lateral Flexion, Right Hip Adduction, and Left Hip Abduction.

• Right Transverse Rotation: Accompanied by Left Lumbar Transverse Rotation, Right Hip Internal Rotation, and Left Hip External Rotation.

• Left Transverse Rotation: Accompanied by Right Lumbar Transverse Rotation, Right Hip External Rotation, and Left Hip Internal Rotation.

Individual Muscle Profiles

• Iliopsoas Muscle (Psoas Major, Minor, and Iliacus):     * Origin: Lower borders of transverse processes of $L1-5$, sides of bodies of $T12-L5$, and inner surface of the ilium.     * Insertion: Lesser trochanter of femur (Psoas major/Iliacus); Pectineal line and iliopectineal eminence (Psoas minor).     * Action: Hip Flexion and External Rotation.

• Rectus Femoris Muscle:     * Origin: Anterior inferior iliac spine (AIIS) and groove above the acetabulum.     * Insertion: Superior aspect of the patella and patellar tendon to the tibial tuberosity.     * Action: Hip Flexion and Knee Extension.

• Sartorius Muscle:     * Origin: Anterior superior iliac spine (ASIS) and notch just below.     * Insertion: Anterior medial condyle of tibia.     * Action: Hip Flexion, External Rotation, and Knee Flexion.

• Tensor Fasciae Latae (TFL) Muscle:     * Origin: Anterior iliac crest and surface of ilium just below crest.     * Insertion: One-fourth of the way down the thigh into the iliotibial tract (IT band), then to Gerdy’s tubercle.     * Action: Hip Flexion and Abduction.

• Gluteus Medius Muscle:     * Origin: Lateral surface of ilium just below crest.     * Insertion: Posterior and middle surfaces of the greater trochanter.     * Action: Abduction, External Rotation, and Internal Rotation.

• Gluteus Minimus Muscle:     * Origin: Lateral surface of ilium below the gluteus medius origin.     * Insertion: Anterior surface of the greater trochanter.     * Action: Internal Rotation and Abduction.

• Gluteus Maximus Muscle:     * Origin: Posterior crest of ilium, sacrum/coccyx near ilium, and lumbar fascia.     * Insertion: Oblique ridge on lateral surface of greater trochanter and IT band.     * Action: Extension and External Rotation.

• Six Deep Lateral Rotator Muscles: Piriformis, Gemellus Superior, Obturator Internus, Gemellus Inferior, Obturator Externus, and Quadratus Femoris.     * Mnemonic: "Pretty Girls Often Get Obnoxious Questions."

• The Hamstring Group:     * Semitendinosus: Originates at ischial tuberosity; inserts upper anterior medial surface of tibia; performs Hip Extension, Internal Rotation, and Knee Flexion/Internal Rotation.     * Semimembranosus: Originates at ischial tuberosity; inserts posteromedial surface of medial tibial condyle; performs Hip Extension, Internal Rotation, and Knee Flexion/Internal Rotation.     * Biceps Femoris: Long head (ischial tuberosity) and Short head (linea aspera); inserts lateral condyle of tibia and head of fibula; performs Hip Extension and External Rotation, and Knee Flexion/External Rotation.

• The Adductor Group:     * Mnemonic for Superior to Inferior: "Peanut Butter Leaves Me Greasy."     * Pectineus: Originates front of pubis; inserts below lesser trochanter; performs External Rotation, Adduction, and Flexion.     * Adductor Brevis: Originates inferior pubic ramus; inserts pectineal line and linea aspera; performs Adduction and External Rotation.     * Adductor Longus: Originates anterior pubis; inserts middle third of linea aspera; performs Adduction.     * Adductor Magnus: Originates ramus of pubis/ischium and ischial tuberosity; inserts whole length of linea aspera and adductor tubercle; performs Adduction and External Rotation.     * Gracilis: Originates medial edge of descending ramus of pubis; inserts anterior medial surface of tibia; performs Adduction, Hip Internal Rotation, and Knee Flexion.

Anatomy, Deformities, and Syndromes

• Inguinal Ligament: Key structural landmark in the groin area.

• Leg Length Discrepancy: Differences in the length of the lower limbs.

• Coxa Deformities (Angle of Inclination):     * Coxa Norma: Normal angle of inclination.     * Coxa Vara: Abnormally decreased angle of inclination.     * Coxa Valga: Abnormally increased angle of inclination.     * Coxa Plana: Also known as Legg-Perthes disease.

• Lower Cross Syndrome:     * Tight Pelvis/Back: Tight Erector Spinae and Tight Hip Flexors.     * Weak Pelvis/Back: Weak Abdominals and Weak Gluteus Maximus.

• Trendelenburg Test:     * Used to assess the integrity of the abductors of the thigh.     * A positive Trendelenburg's sign occurs when the pelvis drops on the side of the lifted leg due to paralyzed or weak abductors on the standing side.